全排列和全组合

public class TestPermutation {

public static void main(String[] args) {
int[] ia = { 1, 2, 3, 4, 5, 6, 7, 8 };

System.out.println("排列结果 : ");

//permutation(ia, n);
System.out.println("组合结果 : ");
for (int i = 1; i <= ia.length; i++) {
int n = i;
combination(ia, n);
}

}

public static void permutation(int[] ia, int n) {
permutation("", ia, n);
}

public static void permutation(String s, int[] ia, int n) {
if (n == 1) {
for (int i = 0; i < ia.length; i++) {

System.out.println(s + ia[i]);
}
} else {
for (int i = 0; i < ia.length; i++) {
String ss = "";
ss = s + ia[i] + ", ";
//建立没有第i个元素的子数组
int[] ii = new int[ia.length - 1];
int index = 0;
for (int j = 0; j < ia.length; j++) {
if (j != i) {
ii[index++] = ia[j];
}
}

permutation(ss, ii, n - 1);
}
}
}

public static void combination(int[] ia, int n) {
combination("", ia, n);
}

public static void combination(String s, int[] ia, int n) {
if (n == 1) {
for (int i = 0; i < ia.length; i++) {
System.out.println(s + ia[i]);
}
} else {
for (int i = 0; i < ia.length - (n - 1); i++) {
String ss = "";
ss = s + ia[i] + ", ";
//建立从i开始的子数组
int[] ii = new int[ia.length - i - 1];
for (int j = 0; j < ia.length - i - 1; j++) {
ii[j] = ia[i + j + 1];
}

combination(ss, ii, n - 1);
}
}

}

}